Ionic liquids are organic salts with melting points below 100° C. and typically are liquids at room temperature. Early interest in the compounds was based upon their conductivity, as described in U.S. Pat. No. 4,764,440. Ionic liquids may be used as a solvent in a chemical vapor deposition system (U.S. Published Patent Application No. 2002/0001674), as coupler solvents in photothermographic systems (U.S. Pat. No. 6,531,270), as solvents for Friedel-Crafts and Diels-Alder reactions (U.S. Pat. No. 6,573,405), as a catalyst for isomerisation reactions, (U.S. Published Patent Application No. 2003/0109767), as complexing agents in separations (U.S. Published Patent Application No. 2003/0125599 and U.S. Pat. No. 6,623,659) as a solvent to form regenerated cellulose (U.S. Published Patent Application No. 2003/0157351), and as a polymerization catalyst (WO 03/087390), to name a few.
Ionic liquids may be made by the reaction of an onium chloride with a Lewis acid such as AlCl3. Heterocyclic halides react with lithium borates in acetonitrile to form ionic liquids useful in electrochemical cells (U.S. Published Patent Application No. 2002/0015883) and with lithium trifluorophosphates to form inert solvents (U.S. Published Patent Application No. 2002/0015884). EMICI (1-methyl-3-ethyl imidazolium chloride) may be reacted with potassium bis-fluorosulfonimide (KFSI) to yield a conductive liquid useful as a current collector (U.S. Pat. No. 6,365,301). Sulfonated or carboxylated triesters of phosphorous acid may serve as anions for ammonium cations (U.S. Published Patent Application 2002/0161261). Salts of diazonium, sulfonium, iodonium or metallocennium types may be useful in chiral syntheses (U.S. Pat. No. 6,548,567).
An aqueous nitrate of Ag(I) may be reacted with an imidazolium chloride to form an ionic liquid and a silver chloride salt (U.S. Pat. No. 6,379,634). A halide-free ionic liquid may be obtained by reacting a halide salt of an organic cation with a Br{acute over (ø)}nsted acid in an alcohol or hydrocarbon solvent (WO 03/051874).
A two-step continuous process is disclosed in WO 03/089389. WO 03/093246 describes liquids wherein the cation is a nitrogen or phosphorous compound and the anion is a five-member nitrogen heterocycle. A process to minimize halides in ionic liquids is based on fluorinated esters or alkyl sulfonates as replacements for haloalkanes when forming an imidazolium salt (U.S. Published Patent Application No. 2003/0080312) and lower melting temperatures have been obtained when the cation is Zn, Sn or Fe (III) and the anion is a quaternary amine (U.S. Pat. No. 6,573,405).
Chiral ionic liquids may be made from optically active ammonium cations and used for asymmetric syntheses (U.S. Published Patent Application No. 2003/0149264). Metallic cations and perhalogenated substituents on the anionic portion are disclosed in U.S. Pat. No. 6,620,546.
In consideration of the many uses for ionic liquids, a need exists for liquids with different properties with new uses and for new ways to make them.